1. Field of the Invention
The present invention relates to communication networks such as local area networks for computers and in particular to hubs within such networks through which the communication traffic passes.
2. The Prior Art
As is well-known in local area networks, computers may be connected to each other to enable them to communicate by way of a hub. The simplest form of communications hub is what is known as a repeater. A repeater typically has a number of ports, to each of which a computer may be connected via an appropriate cable. Any communications sent by a computer would therefore be received by the repeater The repeater simply retransmits any communication received on any port to all of the other ports, thereby enabling the communication to be received by all the other computers connected to the repeater. This is the very simplest form of network and it is possible to extend the network by connecting two, or possibly more, repeaters together via their ports and other networking hubs and equipment can be connected together to form a network in well-known ways. A full description of this is not necessary for understanding the present invention and therefore will not be given here.
Communications take place on such a network according to particular protocols, and one type of protocol is a collision detect multiple access (CDNIA) protocol, of which Ethernet is a well-known example. In such protocols, whenever a communications source such as a computer has a communications packet it wishes to transmit it simply starts to transmit it to the network. In the event that there are no other communications occurring at the time, the communications packet simply passes successfully across the network to the desired destination. If however, another communications packet is being transmitted to the network at the same time then a collision occurs which is detected by both or all transmitting sources and it is determined that the packet has not been sent successfully. After appropriate time another attempt is made to transmit the packet. Such systems work relatively well if properly designed so that there is sufficient network band width to transmit all of the desired communications and, although some collisions are inevitable, if the number of collisions is kept at a relatively low level then the overall communication system is relatively efficient.
To assist in the monitoring of the usage of a network by a network user or manager, it is known to provide a visual indication on a communication hub such as a repeater of the amount of network activity which is occurring and the number of collisions which take place.
For example, it has been known to provide a repeater with an LED indicator which can be activated to be either green or yellow. While there is no activity on the network the indicator is kept switched off. When there is activity on the network the indicator is activated to be green, and when a collision occurs the indicator is activated to be yellow. Such an arrangement has been found to work relatively well in a repeater operating in a network in which communications occur at a speed of 10 megabits a second (10 MB). In such an arrangement if the indicator is simply activated green or yellow during the times when activity and collision respectively are occurring a fairly reasonable visual indication of the usage of the network is given. That is, as network activity increases the indicator is on for an increasing proportion of the time and, as the number of collisions increases, the proportion of the on time for which the indicator is yellow increases.
More recently there have been defined standards of communication in computer networks which permit communications to occur at high speeds, and in particular computer networks operating at 100 MB are now in operation. In such a system, if a visual indicator of the type outlined above is used and it is attempted simply to activate a two colour indicator as outlined above during the times when activity and collision is occurring, then a useful visual output is no longer obtained. This is due to the increased communication speed which has the effect that periods of activity and collision last for much shorter periods of time so that the response times of the indicator and the human eye are not capable of interpreting the output sensibly. For instance, if many collisions were occurring on such a network but all separated in time then it may be that the indicator would never be perceived as indicating yellow but in fact the number of collisions may be dangerously high. Such problems in providing a visual display will simply be compounded by any future increases in network communication speed.